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Biomedical subjects

T Zhang

Publications and source records attributed to T Zhang.

At least 73 records · Page 4Linked to original sources
PubMed2001

Counter-current chromatographic separation of glycoprotein components from Morchella esculenta (L.) with a polymer phase system by a cross-axis coil planet centrifuge.

Using a cross-axis coil planet centrifuge, glycoproteins were separated from fermentation media of Morchella esculenta (L.) by high-speed counter-current chromatography. The performance of the apparatus was optimized with four standard proteins including pepsin, lysozyme, ovalbumin and hemoglobin and a polymer phase system composed of 12.5% (w/w) polyethylene glycol 8000 and 25% (w/w) potassium phosphate in distilled water at various pH values. Separations were performed by eluting the lower phosphate-rich phase at a flow-rate of 1.0 ml/min. Under the optimized conditions three glycoprotein components in Morchella esculenta (L.) were resolved within 6 h.

Agaricales↗
PubMed2001

Splenic cathepsin L is maturated from the proform by interferon-gamma after immunization with exogenous antigens.

The processing of foreign protein antigens into peptides requires the participation of various endo/lysosomal proteases in antigen-presenting cells (APCs). In this study, a proenzyme of cathepsin L, procathepsin L, was found to be present in the spleens of naive mice, as demonstrated by immunoblotting. Interestingly, the maturation of cathepsin L from procathepsin L was strongly induced when the host BALB/c mice were immunized with ovalbumin or soluble leishmanial antigen, despite the fact that mouse albumin, a kind of self-antigen, did not have such a potential. Furthermore, foreign antigens, but not self-antigens, could increase the activity of cathepsin L, probably being mediated by interferon-gamma, as demonstrated by in vivo and in vitro experiments. As cathepsin L matured, the efficiency of antigen processing was increased in APCs. These results suggest that endo/lysosomal cathepsin L plays an important role in the immune regulation via antigen processing even in peripheral lymphoid tissues as well as in the thymus.

Animals↗
PubMed2001

Effect of cooling rate and partial removal of yolk on the chilling injury in zebrafish (Danio rerio) embryos.

High chilling sensitivity is one of the main obstacles to successful cryopreservation of zebrafish embryos. So far the nature of the chilling injury in fish embryos has not been clear. The aim of this study is to investigate the effect of cooling rate and partial removal of yolk on chilling injury in zebrafish embryos. Zebrafish embryos at 64-cell, 50%-epiboly, 6-somite and prim-6 stages were cooled to either 0 degrees C or -5 degrees C at three different cooling rates: slow (0.3 degrees C/min or 1 degree C/min), moderate (30 degrees C/min), and rapid (approximately 300 degrees C/min). After chilling, embryos were warmed in a 26 degrees C water bath, followed by 3-day culturing in EM at 26 +/- 1 degrees C for survival assessment. When embryos were cooled to 0 degrees C for up to 30 min, 64-cell embryos had higher survival after rapid cooling than when they were cooled at a slower rate. When 64-cell embryos were held at -5 degrees C for 1 min, their survival decreased greatly after both slow and rapid cooling. The effect of cooling rate on the survival of 50%-epiboly and 6-somite embryos was not significant after 1 h exposure at 0 degrees C and 1 min exposure at -5 degrees C. However, rapid cooling resulted in significantly lower embryo survival than a cooling rate of 30 degrees C/min or 1 degree C/min after 1 h exposure to 0 degrees C for prim-6 stage or 1 h exposure to -5 degrees C for all stages. Chilling injury in 64-cell embryos appears to be a consequence of exposure time at low temperatures rather than a consequence of rapid cooling. Results also indicate that chilling injury in later stage embryos (50%-epiboly, 6-somite and prim-6) is a consequence of the combination of rapid cooling and exposure time at low temperatures. Dechorionated prim-6 embryos were punctured and about half of yolk was removed. After 24 h culture at 26 +/- 1 degrees C after removal of yolk, the yolk-reduced embryos showed higher embryo survival than did control embryos after rapid cooling to -5 degrees C for 10 to 60 min. Results suggest that cold shock injury after rapid cooling can be mitigated after partial removal of yolk at the prim-6 stage. These findings help us to understand the nature of chilling sensitivity of fish embryos and to develop protocols for their cryopreservation.

Animals↗
PubMed2001

Ykt6 forms a SNARE complex with syntaxin 5, GS28, and Bet1 and participates in a late stage in endoplasmic reticulum-Golgi transport.

The yeast SNARE Ykt6p has been implicated in several trafficking steps, including vesicular transport from the endoplasmic reticulum (ER) to the Golgi, intra-Golgi transport, and homotypic vacuole fusion. The functional role of its mammalian homologue (Ykt6) has not been established. Using antibodies specific for mammalian Ykt6, it is revealed that it is found mainly in Golgi-enriched membranes. Three SNAREs, syntaxin 5, GS28, and Bet1, are specifically associated with Ykt6 as revealed by co-immunoprecipitation, suggesting that these four SNAREs form a SNARE complex. Double labeling of Ykt6 and the Golgi marker mannosidase II or the ER-Golgi recycling marker KDEL receptor suggests that Ykt6 is primarily associated with the Golgi apparatus. Unlike the KDEL receptor, Ykt6 does not cycle back to the peripheral ER exit sites. Antibodies against Ykt6 inhibit in vitro ER-Golgi transport of vesicular stomatitis virus envelope glycoprotein (VSVG) only when they are added before the EGTA-sensitive stage. ER-Golgi transport of VSVG in vitro is also inhibited by recombinant Ykt6. In the presence of antibodies against Ykt6, VSVG accumulates in peri-Golgi vesicular structures and is prevented from entering the mannosidase II compartment, suggesting that Ykt6 functions at a late stage in ER-Golgi transport. Golgi apparatus marked by mannosidase II is fragmented into vesicular structures in cells microinjected with Ykt6 antibodies. It is concluded that Ykt6 functions in a late step of ER-Golgi transport, and this role may be important for the integrity of the Golgi complex.

Base Sequence↗
PubMed2001

The transcriptional regulator, Arg82, is a hybrid kinase with both monophosphoinositol and diphosphoinositol polyphosphate synthase activity.

The Arg82 gene of Saccharomyces cerevisiae encodes a transcriptional regulator that phosphorylates inositol 1,4,5-trisphosphate [Saiardi et al. (1999) Curr. Biol. 9, 1323-1326]. However, some controversy has surrounded the nature of the reaction products. We now show that Arg82 phosphorylates inositol 1,3,4,5-tetrakisphosphate to inositol pentakisphosphate, which is itself converted to two isomers of diphosphoinositol tetrakisphosphate, one of which has never previously been identified. One of the diphosphoinositol phosphates was further phosphorylated by a yeast cell lysate. We propose that Arg82 is an ancestral precursor of two distinct and specific enzyme families: inositol 1,4,5-trisphosphate kinases and diphosphoinositol polyphosphate synthases.

Amino Acid Motifs↗
PubMed2001

Preparative isolation and purification of acteoside and 2'-acetyl acteoside from Cistanches salsa (C.A. Mey.) G. Beck by high-speed counter-current chromatography.

High-speed counter-current chromatography (HSCCC) was applied to the separation and purification of phenylethanoid glycosides (PhGs) acteoside and 2'-acetylacteoside from Cistanches salsa (C.A. Mey) G. Beck with a quaternary two-phase solvent system composed of ethyl acetate-n-butanol-ethanol-water (4:0.6:0.6:5, v/v). HPLC analyses of the CCC fractions revealed that the two main PhGs were over 98% purity. Their chemical structures were identified by 1H NMR, 13C NMR and MS.

Chromatography, High Pressure Liquid↗
PubMed2001

Activation of mitogen-activated protein kinase phosphatase 2 by gonadotropin-releasing hormone.

The aim of these studies was to identify the signaling mechanism(s) that contribute to GnRH-induced expression of MAPK phosphatase (MKP)-2, a dual specificity phosphatase that selectively inactivates MAPKs. GnRH receptor activation induced MKP-2 expression in both clonal (alphaT3-1) and primary gonadotropes. Activation of PKC isozymes was sufficient and required for MKP-2 induction. Inhibition of the extracellular signal-regulated kinase (ERK) or c-Jun N-terminal kinase (JNK) but not the p38 MAPK cascade was sufficient to block GnRH-induced MKP-2 expression. Induction of MKP-2 by GnRH was dependent on elevation in intracellular Ca(2+). Inhibition of Ca(2+) influx through L-type voltage-gated calcium channels blocked GnRH-induced MKP-2 expression. Depletion of intracellular Ca(2+) stores with thapsigargin blocked MKP-2 activation by GnRH independent of ERK and JNK activity. These results support the conclusion that MKP-2 induction by GnRH occurs via MAPK-dependent and -independent pathways. One mechanism requires GnRH-induced ERK and JNK activation, while a second MAPK-independent pathway requires a thapsigargin-sensitive calcium signal.

Animals↗
PubMed2001

Synthesis of 7,8-disubstituted benzolactam-V8 and its binding to protein kinase C.

7-Methoxy-8-decynyl-benzolactam-V8 4 is synthesized using a catalytic asymmetric alkylation reaction as a key step. This compound shows potent activity to three PKC isozymes tested (Ki =45.6, 91.1, and 121.3 nM to PKCalpha, delta, and epsilon, respectively), indicating that introduction of a suitable substituent at the 7-position of 8-decynyl-benzolactam-V8 only slightly reduces the PKC binding affinity.

Binding, Competitive↗
PubMed2001

High-speed counter-current chromatography separation and purification of resveratrol and piceid from Polygonum cuspidatum.

High-speed counter-current chromatography (HSCCC) was applied to the separation and purification of resveratrol and piceid from the dried roots (20.0 g) of Polygonum cuspidatium. The EtOAc extracts were separated with chloroform-methanol-water (4:3:2, v/v). Resveratrol was identified in fraction 5. The water extracts were separated first with EtOAc-EtOH-water (10:1:10, v/v) and then with the same solvent system at the modified volume ratio of 70:1:70. Yields of resveratrol and piceid obtained were 2.18% and 1.07%. Chemical structures of the purified resveratrol and piceid were confirmed by electrospray ionization MS and 1H nuclear magnetic resonance spectroscopy.

Chromatography, High Pressure Liquid↗
PubMed2001

A visuomotor reaction time task increases the irregularity and complexity of inspiratory airflow pattern in man.

Previous studies have suggested that motor cortex may be involved in complex control of respiration in man. In this study, we estimated the influence of a simple visuomotor reaction time task (VMT) on the inspiratory airflow curve (IFC) by comparing measurements of standard deviation (SD), C(0) complexity and approximate entropy (ApEn) of the IFC at rest and during VMT conditions. It was found that both C(0) complexity and ApEn, but not SD of the IFC were significantly increased during the VMT challenge. The results suggest that visuomotor pathways may modulate respiratory motor pathways, because an increase in ApEn is suggestive of increased coupling or communication between (motor) systems.

Entropy↗
PubMed2001

Locating the genes underlying a simulated complex disease by discriminant analysis.

The purpose of this study was to propose and evaluate a novel multivariate approach for genetic mapping of complex binary human diseases. This approach uses the application of either of two methods of standard (stepwise) discriminant analysis to detect linkage based on the differential marker identity-by-descent distributions among the three affection groups of sib pairs (concordantly affected, discordant, and concordantly unaffected). One of the advantages of this approach is that it allows for simultaneously testing all markers, as well as other genetic and environmental factors, in a single multivariate setting. We have explored its properties and behaviors via an application to the simulated data in Genetic Analysis Workshop 12.

Chromosome Mapping↗
PubMed2001

Phylogenetic diversity of a SRB-rich marine biofilm.

This study was conducted to characterize the phylogenetic diversity of a corrosive marine biofilm based on 16S rDNA. Results of phylogenetic analysis indicated that, out of the 112 clones developed, 52 clones (46.4%) were affiliated with two families of sulfate-reducing bacteria: Desulfovibrionaceae and Desulfobacteriaceae. Another 44 clones (39.3%) were affiliated with the Clostridiaceae family of low G+C, gram-positive bacteria. Three clones (2.7%) were closely related to Chlorobium vibrioforme, a green sulfur bacterium.

Base Sequence↗
PubMed2001

Nature of cerium(III)- and lanthanum(III)-induced aggregation of human erythrocyte membrane proteins.

To clarify the nature of the aggregation of membrane proteins (MP) induced by lanthanide cations (Lns), the interaction of cerium(III) (Ce3+) and lanthanum(III)(La3+) with erythrocyte membrane proteins was studied by means of SDS-PAGE, light scattering measurement, fluorescence, CD and FTIR spectra. The results showed that Ce3+ and La3+ induce protein aggregation not only by Lns non-covalent binding and cross-linking, but also by oxidative cross-linking through disulfide bond formation. As demonstrated by intrinsic fluorescence, CD and FTIR spectra studies, the aggregation was accompanied by the conformation changes with tryptophane residues exposing to more hydrophobic environment and the decreasing alpha-helix and beta-sheet contents. By stopped-flow studies, protein aggregation was shown to be a slow change, which is initiated by rapid Lns binding and then followed by subsequent conformational changes.

Blood Proteins↗
PubMed2001

Early growth-response factor 1 and basic transcriptional element-binding protein 2 expression in cardiac allografts.

Early growth-response factor 1 (Egr-1) and basic transcriptional element-binding protein 2 (BTEB2) are transcriptional factors that regulate multiple genes involved in phenotypic changes of smooth muscle cells (SMCs), one of the outstanding pathologic features of chronic cardiac allograft rejection. In this study, we used a heterotopic abdominal heart transplant model in monkeys to evaluate the roles of these molecules in graft coronary vasculopathy. We demonstrated that Egr-1 and BTEB2 are induced in vascular SMCs of rejected cardiac allografts well before morphologic changes, such as intimal thickening. These findings suggest that expression of Egr-1 and BTEB2 is one of the initial events in allograft angiopathy.

Animals↗
PubMed2001

Granule-dependent killing of Toxoplasma gondii by CD8+ T cells.

Immunization of mice with live bradyzoites of a low-virulent Beverley strain of Toxoplasma gondii has been shown to increase CD8+ T-cell mediated immunity against a highly virulent RH strain. We found that preimmunization with an RH homogenate further enhanced this immunity. Using this model, we investigated the mechanism of CD8+ T-cell mediated protection against T. gondii infection. Splenic cells from mice immunized with RH homogenate and live bradyzoites stimulated apoptosis of RH-infected J774A.1 macrophages in vitro, and at the same time, the immunization significantly suppressed the proliferation of parasites within macrophages, as assessed by measuring 3H-uracil uptake by the parasites. Splenic cells from the immunized mice produced larger amounts of interferon-gamma (IFN-gamma) than did naive splenic cells; however, the production of nitric oxide (NO) by RH-infected macrophages was not enhanced. The elimination of CD8+ T cells from splenic cells significantly reduced their inhibitory action on parasite proliferation as well as their cytotoxic activity against RH-infected macrophages, but it did not affect the production of IFN-gamma. Treatment of CD8+ T-enriched splenic cells from the immunized mice with concanamycin A, but not an anti-Fas ligand monoclonal antibody, significantly reduced their anti-proliferative and killing capabilities, suggesting that the CD8+ T cells induced by immunization with RH antigen and live bradyzoites of the Beverley strain may exert protection against T. gondii infection at least in part through granule-dependent cytotoxic activities.

Animals↗
PubMed2001

Retinoic acid-induced blr1 expression requires RARalpha, RXR, and MAPK activation and uses ERK2 but not JNK/SAPK to accelerate cell differentiation.

Upstream signaling requirements of retinoic acid (RA)-induced blr1 expression and downstream signaling consequences of blr1 over-expression in a human myeloid leukemia cell line demonstrate that mitogen-activated protein kinase (MAPK) signaling complexes are involved in both avenues. RA-induced myeloid differentiation and G1/G0 growth arrest of HL-60 cells is known to require the activation of the RARalpha and RXR retinoid receptors, as well as activation of the MAPK, ERK2. Transcriptional activation of the Burkitt's lymphoma receptor 1 (blr1) gene occurs early during RA-induced differentiation of HL-60 cells and requires these same three activating processes. The use of retinoid ligands that activate either the RARalpha or the RXR retinoid receptors revealed that blr1 mRNA induction was detectable only when both RARalpha and RXR were activated. Neither the RARalpha nor RXR selective ligands alone induced expression of blr1, but the combination of the two ligands induced the expression of blr1 to the same extent as RA. The MAPKK (MEK) inhibitor, PD98059, was used to determine whether extracellular signal-regulated kinase (ERK2) activation was necessary for induction of blr1 mRNA. PD98059 inhibited induced blr1 mRNA expression, due to RA or activated RARalpha plus RXR ligands, indicating that ERK2 activation is necessary for blr1 mRNA expression. Previous studies showed that ectopic expression of blr1 also caused increased MAPK activation, in particular ERK2, and subsequently accelerated RA-induced differentiation and G1/G0 growth arrest. Inhibition of ERK2 activation inhibited differentiation of blr1 transfectants, suggesting that the accelerated differentiation reflected blr1-enhanced ERK2 activation. The present data also demonstrate that ectopic expression of blr1 increased JNK/SAPK activity, but JNK/ SAPK activation was not needed for accelerated RA-induced differentiation and growth arrest. The results show that the signals known to be required for HL-60 differentiation, activated RARalpha, RXR, and ERK2, are necessary for blr1 mRNA expression. Downstream consequences of blr1 overexpression include enhanced MAPK signaling.

Cell Differentiation↗
PubMed2001

Promoter Extraction from GenBank (PEG): automatic extraction of eukaryotic promoter sequences in large sets of genes.

UNLABELLED: Promoter Extraction from GenBank (PEG) extracts promoter sequences for large sets of genes using information present in GenBank. For a gene whose promoter sequence is not found, PEG will attempt to extract promoter sequences of the orthologous genes instead. AVAILABILITY: It is freely available to academic users at ftp://cshl.org/pub/science/mzhanglab/theresa/. CONTACT: zhangt@cshl.org; mzhang@cshl.org

Databases, Nucleic Acid↗